[task/code-sniffer] Move code sniffer below build folder.

PHPBB3-11980
[task/code-sniffer] Add PHP CodeSniffer dependency to composer.

PHPBB3-11980
[task/code-sniffer] Phing target for sniffing.

PHPBB3-11980
[task/code-sniffer] Run code sniffer in PHP 5.5 / MySQL Travis CI environment.

PHPBB3-11980